Hoses, particularly flexible hoses, that are used to transmit sewage, such as on boats, recreational vehicles, or the like, often have the problem of transmitting noxious odors from the sewage to the surrounding environment. This has been a major problem in the industry, and much research is done to attempt to find materials which will not transmit noxious odors. However in order to properly test such hoses it is necessary to develop a testing procedure that is cost-effective and accurate.
According to the present invention the fluids which cause the noxious odors which permeate conventional hoses have been identified as sulfur-containing gases, such as carbon disulfide, dimethyl sulfide, and/or dimethyl disulfide (typically all existing at once with carbon disulfide predominating). Using this information, as well as commercially available materials, a procedure has been developed which allows efficient yet effective testing of hose samples. The testing procedure according to the present invention is not only relatively simple, accurate, and cost-effective, it also allows testing to be performed in an accelerated manner. This reduces the time for testing without sacrificing accuracy. Testing can be conducted as long as necessary, and the invention makes it easy to compare the noxious gas permeability of different types of hoses to ensure the best ones are selected (even if none of the hoses are completely resistant to transmission of noxious odors).
According to one aspect of the present invention it has been recognized that methyl alcohol is effective to accelerate the rate of failure of hoses, such as flexible hoses made of PVC (rigid PVC is not permeable). If a hose is conditioned with methyl alcohol the conditioning will not cause the hose to fail if it would otherwise not fail, it merely accelerates the rate of failure. For example without conditioning it may take two weeks for a hose to transmit enough noxious gas that 10 ppm of carbon disulfide is detected. With conditioning the same hose could fail in three days with 40 ppm detected. If the test hose does not fail with conditioning, it most likely will not fail at all.
According to one aspect of the present invention a method of testing hose samples to determine the permeability thereof when used to conduct sewage, each hose sample including a tubular body with open ends, an interior volume, and an exterior surface, is provided. The method comprises the steps of: (a) Sealing the open ends of the hose sample. (b) Introducing methyl alcohol into the hose sample interior volume and allowing it to stand in the hose sample for at least about twenty four hours, and then emptying the alcohol from the hose sample. (c) Introducing fluid which comprises or produces sulfur-containing noxious gases into the hose sample interior volume and allowing the fluid containing hose sample to stand for at least about twenty four hours; and then (d) after about twenty four hours or more, determining whether or not any sulfur-containing gas from the fluid introduced in step (c) has passed through the hose tubular body.
According to the invention a particularly advantageous and effective manner of determining whether there has been permeation of the hose sample with noxious odor gases is provided. According to this aspect of the invention a method of testing the hose samples, as generally called for above, to determine the permeability thereof to noxious odors when used to conduct sewage, is provided. This method comprises the steps of: (a) Sealing the open ends of the hose sample tubular body. (b) Covering the tubular body with a flexible generally (although not necessarily completely) sulfur-containing gas-impervious material, to define a gas volume between the exterior surface of the tubular body and the gas-impervious material. (c) Introducing fluid carbon disulfide, dimethyl sulfide, dimethyl disulfide, or combinations thereof, into the interior volume of the tubular body, and allowing the sealed tubular body to stand for at least about twenty four hours. And then (d) after about twenty four hours or more, evaluating the content of any gas in the gas volume between the exterior surface of the tubular body and the gas impervious material to see if any of the gas in the gas volume is from fluid introduced in step (c) [and typically rejecting the hose sample if it is, or is more than a certain amount].
Step (d) may be repeated several times until fluid introduced into step (c) is detected in the gas volume, or the hose sample is considered to be substantially impermeable (for the use intended) to the fluid introduced in step (c) and therefore has passed the test.
Each time step (d) is practiced it may be practiced utilizing a detector tube and evacuating pump. A slit is made in the gas impervious material (such as nylon film) just large enough for an end of the detector tube to be inserted into the gas volume, the detector tube is hooked up to the evacuating pump, and the pump is operated to draw gas from the gas volume into the detector tube. After completion of step (d) the tube is withdrawn from the slit and the slit is sealed as by covering it with a gas impervious self-adhesive tape. Normally the fluid introduced in step (c) includes a significant quantity of carbon disulfide and a detector tube detects carbon disulfide, so that step (d) is practiced to detect carbon disulfide in the gas volume. A Drager tester is typically employed.
Step (c) may be practiced by introducing into the hose sample interior volume either gas or liquid having a ratio-by-volume of about two parts carbon disulfide and about one part each dimethyl sulfide and dimethyl disulfide. When the reagents are introduced as liquid, typically only about 1.0 ml liquid is necessary.
Typically stop (d) is practiced by allowing the sealed hose sample to stand for about three-six days at ambient conditions (and the same amount of time between each subsequent test), which is sufficient time if the hose is conditioned with methyl alcohol as described earlier. Normally a hose sample is about twelve inches in length, and about one pint of methyl alcohol is introduced into and then removed from the hose sample to condition it, the methyl alcohol normally remains in the hose about three-six days.
It is the primary object of the present invention to effectively test hose samples to determine the permeability thereof to noxious odors when used to conduct sewage. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.